Settable drilling fluids comprising cement kiln dust

ABSTRACT

Settable drilling fluids that comprise an aqueous-based drilling fluid and cement kiln dust. Methods of cementing in a subterranean formation that comprise providing a settable drilling fluid comprising an aqueous-based drilling fluid and cement kiln dust, introducing the settable drilling fluid into a subterranean formation, and allowing the settable drilling fluid to set in the subterranean formation. Methods of converting an aqueous-based drilling fluid to a settable drilling fluid that comprise providing the aqueous-based drilling fluid, and adding cement kiln dust to the aqueous-based drilling fluid to form the settable drilling fluid. Methods of drilling a well bore and cementing a well bore that comprise drilling a well bore, circulating an aqueous-based drilling fluid in the well bore during the step of drilling the well bore, adding cement kiln dust to the aqueous-based drilling fluid to form a settable drilling fluid, and allowing the settable drilling fluid to set in the well bore.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is related to U.S. patent application Ser. No.______, Attorney Docket No. HES 2005-IP-017636U10 entitled “Methods ofUsing Settable Drilling Fluids Comprising Cement Kiln Dust,” filed onthe same date herewith, the entire disclosure of which is incorporatedherein by reference.

BACKGROUND

The present invention relates to subterranean operations and, moreparticularly, to settable drilling fluids that comprise an aqueous-baseddrilling fluid and cement kiln dust (“CKD”), and associated methods ofuse in subterranean operations.

During the drilling of a well bore in a subterranean formation, adrilling fluid may be used to, among other things, cool the drill bit,lubricate the rotating drill string to prevent it from sticking to thewalls of the well bore, prevent blowouts by serving as a hydrostatichead to counteract the sudden entrance into the well bore of highpressure formation fluids, and remove drill cuttings from the well bore.A drilling fluid may be circulated downwardly through a drill pipe anddrill bit and then upwardly through the well bore to the surface. Avariety of drilling fluids may be used during the drilling of well boresinto a subterranean formation. For instance, the drilling fluid used maybe any number of fluids (gaseous or liquid) and mixtures of fluids andsolids (such as solid suspensions, mixtures, and emulsions).

Once the well bore has been drilled to a desired depth, the drill stringand drill bit may be removed from the well bore and the drilling fluidmay be left in the well bore to provide hydrostatic pressure on theformation penetrated by the well bore, e.g., to prevent the flow offormation fluids into the well bore. Next, a pipe string (e.g., casing,liners, etc.) may be introduced into the well bore. Depending on thedepth of the well bore and whether or not any problems are encounteredin introducing the pipe string into the well bore, the drilling fluidmay remain relatively static in the well bore for a relatively long timeperiod, for example, up to 24 hours or longer. While drilling fluids arenot settable (e.g., they generally do not to form a hardened mass overtime), drilling fluids may increase in gel strength over time. Asreferred to herein, “gel strength” is the measure of the ability of acolloidal dispersion to form a gel and is based upon its resistance toshear. Accordingly, during the time period that the drilling fluid isstatic in the well bore, portions of the drilling fluid may increase ingel strength so that displacement of the drilling fluid from within thewell bore may become more difficult.

After the pipe string has been introduced into the well bore, the pipestring may be cemented in the well bore by pumping a cement compositioninto an annular space between the walls of the well bore and the pipestring disposed therein, thereby displacing the drilling fluid in theannulus. However, if the drilling fluid has developed sufficient gelstrength due to remaining static in the well bore, portions of thedrilling fluid in the annulus may not be displaced. Since the drillingfluid generally is not settable, this may be problematic. For example,because the drilling fluid may remain on the surfaces of thesubterranean formation and on the surfaces of the pipe string, asuitable bond between the cement composition and the surfaces may notresult. This may lead to the loss of zonal isolation, which can resultin formation fluids continuing to enter and flow in the well bore.

In order to solve the above-described problem, settable drilling fluidshave been used heretofore. Generally, a settable drilling fluid shouldbe formulated so that it is compatible with drilling fluid (if any)remaining in the well bore. In some instances, the settable drilling maybe formulated using at least a portion of the drilling fluid that wasused in the drilling of the well bore. Because the settable drillingfluid should be compatible with any fluids remaining in the well bore,use of a settable drilling fluid in subsequent cement operations (e.g.,primary cementing) may reduce the problems associated withincompatibility between a cement composition and the drilling fluidremaining in the well bore. Additionally, use of a settable drillingfluid may alleviate problems associated with disposal of the useddrilling fluid.

During the manufacture of cement, a waste material commonly referred toas “CKD” is generated. “CKD,” as that term is used herein, refers to apartially calcined kiln feed that is typically removed from the gasstream and collected during the manufacture of cement. Usually, largequantities of CKD are collected in the production of cement, and theyare commonly disposed of as waste. Disposal of the waste CKD can addundesirable costs to the manufacture of the cement, as well as theenvironmental concerns associated with its disposal. The chemicalanalysis of CKD from various cement manufactures varies depending on anumber of factors, including the particular kiln feed, the efficienciesof the cement production operation, and the associated dust collectionsystems. CKD generally may comprise a variety of oxides, such as SiO₂,Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, and K₂O.

SUMMARY

The present invention relates to subterranean operations and, moreparticularly, to settable drilling fluids comprising an aqueous-baseddrilling fluid and CKD, and associated methods of use in subterraneanoperations.

An embodiment of the present invention provides a settable drillingfluid that comprises an aqueous-based drilling fluid and cement kilndust.

Another embodiment of the present invention provides a settable drillingfluid that comprises an aqueous-based drilling fluid, cement kiln dust,silica fume, and calcium hydroxide.

Another embodiment of the present invention provides a settable drillingfluid that comprises an aqueous-based drilling fluid, cement kiln dust,a hydraulic cement, silica fume, vitrified shale, and calcium hydroxide.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to subterranean operations and, moreparticularly, to settable drilling fluids comprising an aqueous-baseddrilling fluid and CKD, and associated methods of use in subterraneanoperations.

I. Example Settable Drilling Fluids of the Present Invention

The present invention provides a settable drilling fluid comprising anaqueous-based drilling fluid and CKD. These settable drilling fluidsshould be suitable for use in a variety of subterranean cementingoperations, including, but not limited to, primary cementing. Generally,the settable drilling fluids of the present invention may be formulatedso that it is compatible with the drilling fluid, if any, that remainsin the well bore from the drilling operations previously performed inthe well bore.

Generally, any aqueous-based drilling fluid suitable for use in drillingoperations may be used, provided the drilling fluid, or any componentsthereof, does not adversely interact with the other components of thesettable drilling fluids of the present invention. In some embodiments,the drilling fluid may included at least a portion of the drilling fluidthat was used in drilling the well bore. Suitable aqueous-based drillingfluids include any number of fluids that may be used for drilling a wellbore. An example of a suitable aqueous drilling fluid comprises anaqueous gel. For viscosification, in some embodiments, suitable aqueousgels may comprise a viscosifier, such as clays (e.g, bentonite,attapulgite, sepeolite, etc.) and polymeric viscosifiers. In someembodiments, suitable aqueous gels may comprise a weighting material(e.g., barium sulfate). In some embodiments, suitable aqueous gels maycomprise calcium oxide (e.g., lime muds) and/or partially hydrolyzedpolyacrylamide (“PHPA”) (e.g., PHPA muds). Additionally, suitableaqueous drilling fluids further may comprise any of a variety ofsuitable additives, including, but not limited to, thinners, filtrationcontrol agents, polymeric viscosifiers, caustic soda, salts (e.g.,sodium chloride), and combinations thereof.

In some embodiments, the aqueous-based drilling fluid may be present inthe settable drilling fluids of the present invention in an amount inthe range of from about 5% to about 80% by weight of the settabledrilling fluid. In some embodiments, the drilling fluid may be presentin the settable drilling fluids of the present invention in an amount inthe range of from about 5% to about 40% by weight of the settabledrilling fluid. In some embodiments, the drilling fluid may be presentin the settable drilling fluids of the present invention in an amount inthe range of from about 10% to about 30% by weight of the settabledrilling fluid. One of ordinary skill in the art will be able todetermine, with the benefit of this disclosure, the appropriate amountof the drilling fluid present in the settable drilling fluids of thepresent invention based on a number of factors, including the desiredcompressive strength, downhole temperature, formation permeability,formation porosity, setting of the mud filter cake, and rheology of thefluid.

The CKD should be included in the settable drilling fluid of the presentinvention in an amount sufficient, among other things, to provide thedesired compressive strength for a particular application. In someembodiments, the CKD may be present in the settable drilling fluids ofthe present invention in an amount in the range of from about 5% to 30%by weight of the settable drilling fluid. In some embodiments, the CKDmay be present in the settable drilling fluids of the present inventionin an amount in the range of from about 5% to 20% by weight of thesettable drilling fluid. In some embodiments, the CKD may be present inthe settable drilling fluids of the present invention in an amount inthe range of from about 5% to 15% by weight of the settable drillingfluid.

In some embodiments, the settable drilling fluids of the presentinvention optionally further may comprise additional water. Theadditional water included in the settable drilling fluids of the presentinvention may include freshwater, saltwater (e.g., water containing oneor more salts dissolved therein), brine (e.g., saturated saltwaterproduced from subterranean formations), seawater, or combinationsthereof. Generally, the water may be from any source, provided that itdoes not contain an excess of compounds that may adversely affect othercomponents in the settable composition. In some embodiments, theadditional water may be included in the settable drilling fluids of thepresent invention in an amount in the range of from about 5% to about40% by weight of the settable drilling fluid. In some embodiments, theadditional water may be included in the settable drilling fluids of thepresent invention in an amount in the range of from about 15% to about35% by weight of the settable drilling fluid.

Optionally, in some embodiments, the settable drilling fluids of thepresent invention further may comprise silica fume. Generally, thesilica fume may be included in the settable drilling fluids of thepresent invention in an amount sufficient to provide the desiredcompressive strength. In some embodiments, the silica fume may bepresent in the settable drilling fluids of the present invention in anamount in the range of from about 5% to 20% by weight of the settabledrilling fluid. In some embodiments, the silica fume may be present inthe settable drilling fluids of the present invention in an amount inthe range of from about 8% to 15% by weight of the settable drillingfluid.

Optionally, in some embodiments, the settable drilling fluids of thepresent invention further may comprise a hydraulic cement. A variety ofhydraulic cements may be utilized in accordance with the presentinvention, including, but not limited to, those comprising calcium,aluminum, silicon, oxygen, iron, and/or sulfur, which set and harden byreaction with water. Suitable hydraulic cements include, but are notlimited to, Portland cements, pozzolana cements, gypsum cements, highalumina content cements, slag cements, silica cements, and combinationsthereof. In certain embodiments, the hydraulic cement may comprise aPortland cement. In some embodiments, the Portland cements that aresuited for use in the present invention are classified as Classes A, C,H, and G cements according to American Petroleum Institute, APISpecification for Materials and Testing for Well Cements, APISpecification 10, Fifth Ed., Jul. 1, 1990.

Where present, the hydraulic cement generally may be included in thesettable drilling fluids in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, thehydraulic cement may be present in the settable drilling fluids of thepresent invention in an amount up to about 10% by weight of the settabledrilling fluid. In some embodiments, the hydraulic cement may be presentin the settable drilling fluids of the present invention in an amount inthe range of from 3% to about 7% by weight of the settable drillingfluid.

Optionally, in some embodiments, the settable drilling fluids of thepresent invention further may comprise vitrified shale. Among otherthings, the vitrified shale included in the settable compositions mayreact with excess lime to form a suitable cementing material, forexample, calcium silicate hydrate. A variety of vitrified shales aresuitable, including those comprising silicon, aluminum, calcium, and/ormagnesium. Suitable examples of vitrified shale include, but are notlimited to, PRESSUR-SEAL® FINE LCM material and PRESSUR-SEAL® COARSE LCMmaterial, which are commercially available from TXI Energy Services,Inc., Houston, Tex. Generally, the vitrified shale may have any particlesize distribution as desired for a particular application. In certainembodiments, the vitrified shale may have a particle size distributionin the range of from about 37 micrometers to about 4,750 micrometers.

Where present, the vitrified shale generally may be included in thesettable drilling fluids in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, thevitrified shale may be present in the settable drilling fluids of thepresent invention in an amount up to about 12% by weight of the settabledrilling fluid. In some embodiments, the vitrified shale may be presentin the settable drilling fluids of the present invention in an amount inthe range of from 1% to about 10% by weight of the settable drillingfluid.

Optionally, in some embodiments, the settable drilling fluids of thepresent invention further may comprise calcium hydroxide (commonlyreferred to as “hydrated lime”). In some embodiments, the calciumhydroxide may be present in the settable drilling fluids of the presentinvention in an amount in the range of from about 10% to about 30% byweight of the settable drilling fluid.

Optionally, in some embodiments, the settable drilling fluids of thepresent invention further may comprise a dispersant. While a variety ofdispersants known to those skilled in the art may be used in accordancewith the present invention, a suitable dispersant comprises awater-soluble polymer prepared by the condensation of formaldehyde withacetone and sodium bisulfite. Such a dispersant is commerciallyavailable as CFR™-3 dispersant from Halliburton Energy Services, Inc.,Duncan, Okla. Another suitable dispersant comprises a sodium salt ofnaphthalene sulfonic acid condensed with formaldehyde, an example ofwhich is commercially available as CFR™-2 dispersant also fromHalliburton Energy Services, Inc., Duncan, Okla. Another suitabledispersant comprises gluconic acid, an example of which is commerciallyavailable as CFR™-1 dispersant also from Halliburton Energy Services,Inc., Duncan, Okla. In some embodiments, the dispersant may be presentin the settable drilling fluids of the present invention in an amount inthe range of from about 0.1% to about 5% by weight of the settabledrilling fluid.

Optionally, in some embodiments, the settable compositions of thepresent invention further may comprise a set retarder. As used herein,the term “set retarder” refers to an additive that retards the settingof the settable drilling fluids of the present invention. Examples ofsuitable set retarding additives include, but are not limited to,ammonium, alkali metals, alkaline earth metals, metal salts ofsulfoalkylated lignins, hydroxycarboxy acids, copolymers of2-acrylamido-2-methylpropane sulfonic acid salt and acrylic acid ormaleic acid, and combinations thereof. One example of a suitablesulfoalkylate lignin comprises a sulfomethylated lignin. Suitable setretarding additives are disclosed in more detail in U.S. Pat. No. Re.31,190, the entire disclosure of which is incorporated herein byreference. Suitable set retarding additives are commercially availablefrom Halliburton Energy Services, Inc. under the tradenames HR® 4, HR ®5, HR® 7, HR® 12, HR® 15, HR® 25, SCR™ 100, and SCR™ 500. Generally,where used, the set retarding additive may be included in the settablecompositions of the present invention in an amount sufficient to providethe desired set retardation. In some embodiments, the set retardingadditive may be present in an amount in the range of from about 0.1% toabout 2% by weight of the settable drilling.

Additionally, those of ordinary skill in the art will recognize avariety of additional additives suitable for inclusion in the settabledrilling fluids of the present invention for a particular application.Such additives may include, but are not limited to, accelerators, lostcirculation materials, fluid loss control additives, and combinationsthereof.

II. Example Methods of the Present Invention

The settable drilling fluids of the present invention may be used in anyof a variety of subterranean cementing operations. For example, asettable composition of the present invention that comprises a portionof the drilling fluid used in drilling a well bore may be used incementing operations in the well bore. While the compositions of thepresent invention may be used in a variety of cementing operations, theymay be particularly suitable for primary cementing operations becausethe settable drilling fluids of the present invention generally shouldbe compatible with the drilling fluid, if any, remaining in the wellbore.

An example of such a cementing operation using the settable drillingfluids of the present invention may comprise providing an aqueous-baseddrilling fluid, adding CKD to the aqueous-based drilling fluid to form asettable drilling fluid, introducing the settable drilling fluid into asubterranean formation, and allowing the settable drilling fluid to setin the subterranean formation. As will be understood by those ofordinary skill in the art, with the benefit of this disclosure,additional additives, such as those described above, may be added to thesettable drilling fluid to impart desired properties thereto. In someembodiments, the settable drilling fluids of the present invention maybe used in primary cementing, in that, the cementing embodiments furthermay comprise introducing a casing into a well bore penetrated by thewell bore, wherein the settable drilling fluid sets in an annulus formedbetween the casing and a wall of the well bore.

In some embodiments, the methods of the present invention further maycomprise drilling a well bore while the aqueous-based drilling fluid iscirculated in the well bore. At a desired time during the drillingoperation (for example, when the well bore, or that portion of the wellbore, has been drilled to the desired depth), the aqueous-based drillingfluid may be converted into a settable drilling fluid of the presentinvention. Converting the aqueous-based drilling fluid into a settabledrilling fluid of the present invention generally comprises added CKD tothe drilling fluid. In some embodiments, the CKD may be mixed with waterto form a settable composition, prior to their addition to theaqueous-based drilling fluid. As will be understood by those of ordinaryskill in the art, with the benefit of this disclosure, additionaladditives, such as those described above, may be added to theaqueous-based drilling fluid to impart desired properties thereto. Thissettable drilling fluid may then be used in any suitable cementingoperation.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

EXAMPLE 1

Three aqueous-based drilling fluids having a density of 10 pounds pergallon were prepared. The first drilling fluid was a bentonite mud. Thesecond drilling fluid was a PHPA mud. The third drilling fluid was alime mud. The formulation of each drilling fluid is provided in Table 1below. After preparation, each drilling fluid was stirred on adispersator for at least 60 minutes. Each of these drilling fluids wasmixed with CKD and tested as provided in Examples 2-4. TABLE 1 DrillingFluid Formulations Bentonite PHPA Lime Formulation Mud Mud Mud Water,bbl 0.928 0.913 0.91 Bentonite Viscosifier,¹ lb 15 10 12 SodiumChloride, lb — 35.9 — Thinner,² lb — — 4 Sodium Hydroxide, lb — 0.25 1.5Calcium Hydroxide, lb — — 6 Partially Hydrolyzed Polyacrylamide,³ lb — 1— Filtration Control Agent,⁴ lb — 1 1 Polymer Viscosifier,⁵ lb — 0.250.5 Weighting Material,⁶ lb 75 52 73¹Ground Bentonite available as AQUAGEL ® Viscosifier from HalliburtonEnergy Services, Inc., Duncan, Oklahoma.²A ferrochrome lignosulfonate available as QUIK-THIN ® Thinner fromHalliburton Energy Services, Inc., Duncan, Oklahoma.³A granular synthetic polymer containing PHPA copolymer available as EZMUD DP ® Borehole Stabilizer from Halliburton Energy Services, Inc.,Duncan, Oklahoma.⁴PAC-L ® Modifier Natural Cellulosic Polymer available from HalliburtonEnergy Services, Inc., Duncan, Oklahoma.⁵BARAZAN D PLUS ® Viscosifier available from Halliburton EnergyServices, Inc., Duncan, Oklahoma.⁶A ground barium sulfate available as Bariod ® Weighting Material fromHalliburton Energy Services, Inc., Duncan, Oklahoma.

EXAMPLE 2

Sample settable compositions (Fluid Nos. 1-2) were prepared. The samplesettable compositions comprised water, CKD, silica fume, a dispersant, aset retarder, and calcium hydroxide as shown below in Table 2. TABLE 2Sample Settable Composition Comprising CKD Composition (grams) Fluid No.1 Fluid No. 2 Water 400 400 Class A CKD 150 — Class H CKD — 150 SilicaFume 150 150 Dispersant¹ 50 40 Set Retarder² 13 13 Calcium Hydroxide 300300¹CFR ™-3L Dispersant from Halliburton Energy Services, Inc.²HR ™-4L Retarder from Halliburton Energy Services, Inc.

After preparation of the sample settable compositions, to prepare samplesettable drilling fluids, the sample settable compositions were mixedwith the sample drilling fluids from Example 1 in a volume ratio ofsample settable composition to drilling fluid of about 80:20, as shownbelow in Table 3. Thereafter, the resultant foamed sample compositionswere subjected to 72-hour compressive strength tests at the temperatureindicated in accordance with API Specification 10. The results of thecompressive strength tests are set forth in the table below. TABLE 3Compressive Strength of Sample Settable Drilling Fluids Settable 72 HrComposition Compressive (80 parts Drilling Fluid Temp. Strength by vol)(20 parts by vol) (° F.) (psi) Fluid No. 1 PHPA Mud 80 Not Set 140 284160 385 Fluid No. 2 PHPA Mud 80 Not Set 140 328 160 363 Fluid No. 2Bentonite Mud 80 13.49 140 597 160 191.7 Fluid No. 2 Lime Mud 80 Not Set140 488 160 319

EXAMPLE 3

A sample settable composition (Fluid No. 3) was prepared. Fluid No. 3comprised water, CKD, silica fume, class H Portland cement, adispersant, a set retarder, and calcium hydroxide as shown below inTable 4. TABLE 4 Sample Settable Composition Comprising CKD and PortlandCement Composition (grams) Fluid No. 3 Water 400 Class H CKD 75 SilicaFume 150 Class H Portland Cement 75 Dispersant¹ 40 Set Retarder² 13Calcium Hydroxide 300¹CFR ™-3L Dispersant from Halliburton Energy Services, Inc.²HR ™-4L Retarder from Halliburton Energy Services, Inc.

After preparation, to prepare sample settable drilling fluids, Fluid No.3 was mixed with the sample drilling fluids from Example 1 in a volumeratio of Fluid No. 3 to drilling fluid of about 80:20. Thereafter, theresultant settable drilling fluids were subjected to thickening time and72-hour compressive strength tests at the temperature indicated inaccordance with API Specification 10. The results of the compressivestrength tests are set forth in the table below. TABLE 5 CompressiveStrength/Thickening Time of Sample Settable Drilling Fluids Settable 72Hr Thickening Composition Compressive Time to 70 (80 parts DrillingFluid Temp. Strength BC by vol) (20 parts by vol) (° F.) (psi) (hr:min)Fluid No. 3 Lime Mud 80 25 n/a 140 585 6:22 160 541 n/a Fluid No. 3 PHPAMud 80 15.57 n/a 140 323 n/a 160 279 n/a Fluid No. 3 Bentonite Mud 8018.51 n/a 140 866 3:19 160 699 n/a

EXAMPLE 4

A sample settable composition (Fluid No. 4) was prepared. Fluid No. 4comprised water, CKD, silica fume, vitrified shale, class H Portlandcement, a dispersant, a set retarder, and calcium hydroxide as shownbelow in Table 6. TABLE 6 Sample Settable Composition Comprising CKD,Portland Cement, and Vitrified Shale Composition (grams) Fluid No. 4Water 400 Class H CKD 37.5 Silica Fume 150 Vitrified Shale 37.5 Class HPortland Cement 75 Dispersant¹ 40 Set Retarder² 13 Calcium Hydroxide 300¹CFR ™-3L Dispersant from Halliburton Energy Services, Inc.²HR ™-4L Retarder from Halliburton Energy Services, Inc.

After preparation, to prepare sample settable drilling fluids, Fluid No.4 was mixed with the sample drilling fluids from Example 1 in a volumeratio of Fluid No. 4 to drilling fluid of about 80:20. Thereafter, theresultant settable drilling fluids were subjected to 72-hour compressivestrength tests at the temperature indicated in accordance with APISpecification 10. The results of the compressive strength tests are setforth in the table below. TABLE 7 Compressive Strengths of SampleSettable Drilling Fluid Settable 72 Hr Composition Compressive (80 partsDrilling Fluid Temp. Strength by vol) (20 parts by vol) (° F.) (psi)Fluid No. 4 Lime Mud 80 12.47 140 864 160 676 Fluid No. 4 PHPA Mud 8034.4 140 744 160 713 Fluid No. 4 Bentonite Mud 80 18 140 676 160 717

These examples thus indicate that settable drilling fluids comprising adrilling fluid and CKD may have suitable thickening times and/orcompressive strengths for a particular application.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(of the form, “from about a to about c,” or, equivalently, “fromapproximately a to c,” or equivalently, “from approximately a-c”)disclosed herein is to be understood as referring to the power set (theset of all subsets) of the respective range of values, and set forthevery range encompassed within the broader range of values. Also, theterms in the claims have their plain, ordinary meaning unless otherwiseexplicitly and clearly defined by the patentee.

1. A settable fluid comprising: an aqueous-based drilling fluid thatcomprises: water present in an amount sufficient for using theaqueous-based drilling fluid for drilling in a subterranean formation;and at least one additive selected from the group consisting of aviscosifier, a weighting material, a thinner, and a filtration controlagent; and cement kiln dust.
 2. (canceled)
 3. The settable fluid ofclaim 1 wherein the cement kiln dust is present in the settable fluid inan amount in the range of from about 1% to about 25% by weight of thesettable fluid.
 4. The settable fluid of claim 1 wherein theaqueous-based drilling fluid is a bentonite mud, a lime mud, a partiallyhydrolyzed polyacrylamide mud, or combinations thereof.
 5. The settablefluid of claim 1 wherein the aqueous-based drilling fluid is an aqueousgel comprising a the viscosifier, and wherein the viscosifier isselected from the group consisting of a clay, a polymeric viscosifier,and combinations thereof.
 6. The settable fluid of claim 1 wherein theaqueous-based drilling fluid is present in the settable fluid in anamount in the range of from about 5% to about 40% by weight of thesettable fluid.
 7. The settable fluid of claim 1 wherein the settablefluid comprises at least one additive selected from the group consistingof an accelerator, a lost circulation material, a fluid loss controladditive, a dispersant, a set retarder, calcium hydroxide, silica fume,a hydraulic cement, vitrified shale, and combinations thereof.
 8. Thesettable fluid of claim 1 wherein the settable fluid comprises silicafume in an amount in the range of from about 5% to about 20% by weightof the settable fluid.
 9. The settable fluid of claim 1 wherein thesettable fluid comprises a hydraulic cement in an amount up to about 10%by weight of the settable fluid.
 10. The settable fluid of claim 1wherein the settable fluid comprises vitrified shale in an amount up toabout 10% by weight of the settable fluid.
 11. The settable fluid ofclaim 1 wherein the settable fluid comprises calcium hydroxide in anamount in the range of from about 10% to about 30% by weight of thesettable fluid.
 12. A settable fluid comprising: an aqueous-baseddrilling fluid that comprises: water present in an amount sufficient forusing the aqueous-based drilling fluid for drilling in a subterraneanformation; and at least one additive selected from the group consistingof a viscosifier, a weighting material, a thinner, and a filtrationcontrol agent; and cement kiln dust; silica fume; and calcium hydroxide.13. The settable fluid of claim 12 wherein the cement kiln dust ispresent in the settable fluid in an amount in the range of from about 1%to about 25% by weight of the settable fluid.
 14. The settable fluid ofclaim 12 wherein the aqueous-based drilling fluid is a bentonite mud, alime mud, a partially hydrolyzed polyacrylamide mud, or combinationsthereof.
 15. The settable fluid of claim 12 wherein the aqueous-baseddrilling fluid is present in the settable fluid in an amount in therange of from about 5% to about 40% by weight of the settable fluid. 16.The settable fluid of claim 12 wherein the settable fluid comprises atleast one additive selected from the group consisting of an accelerator,a lost circulation material, a fluid loss control additive, adispersant, a set retarder, a hydraulic cement, vitrified shale, andcombinations thereof.
 17. The settable fluid of claim 12 wherein: thesilica fume is present in an amount in the range of from about 5% toabout 20% by weight of the settable fluid; and the calcium hydroxide ispresent in an amount in the range of from about 10% to about 30% byweight of the settable fluid.
 18. A settable fluid comprising: anaqueous-based drilling fluid that comprises: water present in an amountsufficient for using the aqueous-based drilling fluid for drilling in asubterranean formation; and at least one additive selected from thegroup consisting of a viscosifier, a weighting material, a thinner, anda filtration control agent; and cement kiln dust; a hydraulic cement;silica fume; vitrified shale; and calcium hydroxide.
 19. The settablefluid of claim 18 wherein the cement kiln dust is present in thesettable fluid in an amount in the range of from about 1% to about 25%by weight of the settable fluid.
 20. The settable fluid of claim 18wherein the aqueous-based drilling fluid is a bentonite mud, a lime mud,a partially hydrolyzed polyacrylamide mud, or combinations thereof. 21.The settable fluid of claim 18 wherein the aqueous-based drilling fluidis present in the settable fluid in an amount in the range of from about5% to about 40% by weight of the settable fluid.
 22. The settable fluidof claim 18 wherein the settable fluid comprises at least one additiveselected from the group consisting of an accelerator, a lost circulationmaterial, a fluid loss control additive, a dispersant, a set retarder,and combinations thereof.
 23. The settable fluid of claim 18 wherein:the silica fume is present in an amount in the range of from about 5% toabout 20% by weight of the settable fluid; the hydraulic cement ispresent in an amount up to about 10% by weight of the settable fluid;the vitrified shale is present in an amount up to about 10% by weight ofthe settable fluid; and the calcium hydroxide is present in an amount inthe range of from about 10% to about 30% by weight of the settablefluid.
 24. The settable fluid of claim 1 wherein the settable fluid ispumpable for placement in a space between a pipe string and asubterranean formation.
 25. The settable fluid of claim 12 wherein thesettable fluid is pumpable for placement in a space between a pipestring and a subterranean formation.
 26. The settable fluid of claim 18wherein the settable fluid is pumpable for placement in a space betweena pipe string and a subterranean formation.
 27. The settable fluid ofclaim 1 wherein the settable fluid comprises a mixture of theaqueous-based drilling fluid, the cement kiln dust, and additionalwater.
 28. The settable fluid of claim 12 wherein the settable fluidcomprises a mixture of the aqueous-based drilling fluid, the cement kilndust, the silica fume, the calcium hydroxide, and additional water. 29.The settable fluid of claim 18 wherein the settable fluid comprises amixture of the aqueous-based drilling fluid, the cement kiln dust, thehydraulic cement, the silica fume, the vitrified shale, the calciumhydroxide, and additional water.
 30. The settable fluid of claim 1wherein the aqueous-based drilling fluid is a used aqueous-baseddrilling fluid without excess water removed.